Motion
by EoEDaD
Summary: Force is equal to the change in momentum per change in time. For a constant mass, force equals mass times acceleration. And there is nothing that can be done to change that. SK, 2 of 3.
1. Law 1

I already posted this on my lj, but I just like having everything all neat and pretty and lined up in one place. Plus, I'm a total sucker for reviews. Based on the first of Newton's three laws of motion, because... just because. Because I'm a geek, pretty much.

* * *

**Motion – I**

_Every object persists in its state of rest or uniform motion in a straight line unless it is compelled to change that state by forces impressed on it._

Kamui reread the sentence for the fifth time, working from some vague hope that if he just read the words enough times, they would magically start to assemble themselves into something that made sense (though really, he should have learned by now that magic was never that helpful. If the words in his physics textbook ever magically did anything, it would probably be to leap up and try to eat him). He was so _tired;_ there had been another kekkai to defend last night and while he hadn't gone (the other Seals hadn't wanted to interfere with his schoolwork; his laughter when his teacher told the class the next day that homework wasn't the end of the world was tinged with hysteria), he had stayed up all night worrying about Sorata and Subaru.

Especially Subaru. It wasn't that he didn't care about Sorata, but he could trust the man to look after himself, unless Arashi was involved. Subaru, however…

"Having trouble?"

"Subaru!" Kamui started guiltily as the subject of his thoughts walked into the room. "Hi. Are—are you okay? Did the doctors say you could get up? How's your arm feel?"

Subaru smiled a little. "It's nothing. I'm not even sure how Kigai-san managed to hit me in the first place." He cast a rueful glance at his bandaged wrist.

Kamui crossed his arms. "You didn't answer my question," he told Subaru reproachfully. "The one about the doctors. If you get sick and die because you're not bothering to rest every once in a while, I will be _so_ mad at you. And it would just be ridiculous anyways."

Something in Subaru's smile shifted. "This won't kill me, Kamui," he said gently.

The silence that followed had an oddly heavy quality, as though all that couldn't be said by either of them, Subaru—_but I must eventually, it is Wished twice over, my fate was sealed nine years before I met you—_

and Kamui—_but I couldn't bear that, your absence, you more than any other, I—I—_

_I _care—

it was as though the words permeated the air itself; unsaid but not, perhaps, unheard.

"I know," Kamui muttered eventually, though whether he was responding to the spoken or the unspoken even he didn't know.

Subaru sighed, the sound soft and delicate and almost regretful, and then the strange tension lifted completely and he walked to Kamui's side. "Is that something I can help with?"

Kamui scowled, secretly grateful for the change of subject. "I dunno. I think it's not making any sense, but I can't be sure because to be sure I would have to know what it would look like if it _did._ I swear, they come up with this stuff just to torture us."

He laughed, the almost-laugh that Kamui had come to realize was the closest he would ever get to hearing true amusement from Subaru, and said, "I don't think that's quite it." He leaned a little closer over Kamui's shoulder, and Kamui had to repress a shudder as he felt the vibrations from Subaru's quiet hum in his ear. "Mm. Well, physics work a little differently in onmyoujutsu, but I think…" His voice trailed off, and Kamui could all but feel his thoughts drifting away.

"Eh, it doesn't really matter. The test's a week away—I'll probably get it by then." _After a full night of sleep, and maybe some coffee_. He shut the book and twisted around in his chair to face Subaru properly, resting his chin on the back of it. "You're sure that you're okay?"

"Yes. You don't need to worry about me, you know."

Kamui's eyes narrowed, and he let out a huff of frustration. "Maybe I don't need to, but I _do._ I apologize if it irritates you, but I worry about you and if you're in pain or sad, it makes me sad, too, and that's not going to change and you're not going to convince me to even try."

Subaru's eyes wandered away from his and settled on the black gloves covering his hands. "You shouldn't," he said quietly, almost whispering, and Kamui had to strain to hear him. "Worry about me, or care. I would… be unhappy if I were to hurt you, through that."

Now Kamui's eyes fell, too, and they landed on Subaru's gloves; he understood the symbolism behind them far too well. "But I choose to," he reminded Subaru. "It's a part of—" He hesitated, reconsidered what he was going to say. "—of friendship, that risk, that you will be hurt by someone else's pain, isn't it?"

"Risk?" Subaru was definitely talking to himself now, Kamui realized. "But there is risk and there is certainty, and I am too selfish to give up my certainty—even for this, because that, too, would be a risk." He sounded like the doctors had given him painkillers or something, because normally Subaru would never talk like this, ever.

Kamui wanted to ask what he meant when he said "certainty" with that weirdly happy-sad inflection, but he knew that would be crossing one of the indefinite but so very real lines that were a part of Subaru—the things that were not talked about but danced around, carefully and awkwardly, less choreography than being dropped in a maze and told to find the other end, blindfolded, without touching any of the walls. He had come too close already, he felt, and at any minute Subaru would fall back even farther into his retreat of coldness and distance and polite, formal solitude.

_Every object persists in its state of rest or uniform motion in a straight line…_

He looked at Subaru suddenly, really _looked_ at him, and saw with an almost nauseating surge of fear that Subaru was still staring at his gloves—lovingly—and that in and of itself was painful, to see Subaru so hopelessly attached to someone who hurt him so badly; but worse was a vision of Subaru with the Sakurazukamori's hand through his chest, and him _smiling_, as though this was all that he could ask of the world, to die at the hand of someone special. And then, another image: Subaru alive, the assassin dead, but some part of Subaru dead too and the rest a living, walking corpse—Angel—eye—blood. Every time, so much blood.

That—just—_no._ No, no, no. Never. Kamui didn't know what part of him it was that was rebelling so strongly against the images, and—well, if it was Subaru's Wish—but how could he let Subaru walk into this blindly?

…_uniform motion in a straight line…_

It seemed massively unfair, that the older man would never realize—not really—that there were others who cared about him, who would mourn his death, who would die with him. Oh, Kamui didn't doubt that he knew it on an intellectual level, but it wasn't the_ same_, it wasn't_ knowing_.

Then, how…

…_unless it is compelled to change that state by forces impressed on it._

Subaru looked up, shocked, as Kamui's lips met his.

* * *

I put up a... continuation (not a sequel, not really the same storyline, just happens to be prompted with the second law) at my lj, too, but I really really really want to revise it before I actually do anything else. If anyone's interested: 

http // eoedad . livejournal . com / 1365 . html # cutid1

* * *


	2. Law 2

_Force is equal to the change in momentum per change in time. For a constant mass, force equals mass times acceleration. _

Kamui didn't know what to do.

He _liked_ Subaru, probably more than liked him, but the man had always seemed more god than human, even in his pain. Subaru was always so remote, so beautiful, but not in any way that Kamui could really feel comfortable thinking about, as though it were somehow warped to appreciate something that was the result of so much sorrow and betrayal—now more than ever.

Furtively, appalled by his own irreverence, he touched one trembling fingertip to Subaru's rib. It did not crumble to dust under the contact, as he had half-expected it would, but he snatched his hand back anyways. Subaru's skin was cold, almost icy; the smell of sakura blossoms permeated the room.

The onmyouji—assassin, he guessed, but somehow that thought hurt less than it should—turned a little in his sleep, moaning quietly, and Kamui stared in open fascination at the bones shifting beneath that pale, pale skin. Subaru had gone from thin to emaciated since he had left, and while it did not make him any less striking, there was an edge to his beauty now, lines and points where there should be rounded flesh; stark, harsh, the austere geometry of a canyon cutting through a desert plain. Kamui could not imagine how he had ever had the audacity to think of him as he did, to desire anything more than what Subaru was generous enough to give him. It seemed almost sacrilegious to want this broken god, to think that he could understand or help him—and when had he ever been able to help Subaru, anyways?—but even more so to watch him sleep like this, to unconsciously brush his fingertips along those too-visible cheekbones as he went to check Subaru's temperature, to be so constantly aware of the fact that Subaru's shirt was still drying in the other room, which meant that Subaru was lying shirtless and unconscious _in his bed,_ and even _blushing_ felt like a presumption under those circumstances.

He had been working on his science homework when the bell rang, and he answered the door of the mansion unthinkingly, assuming that one of the others had come back once it started to rain or that Sorata had forgotten his umbrella for the umpteenth time that cold, drizzly week. When he saw who was leaning against the doorframe, wet and visibly ill, he nearly shut it again and went to go catch up on what was obviously some much-needed sleep.

He might have done it, too, never considering that it might be anything more than just a hallucination, if Subaru hadn't focused his eyes on the empty air over Kamui's head. Half-smiling, he had breathed, "Seishiro-san…"

No dream could hurt that much.

So he had opened the door and helped Subaru inside, and that led them to here, Subaru exhausted and feverish and asleep (_in his bed,_ but he's not thinking about that, he's _not_) and Kamui utterly confused and conflicted. None of the others were home, and he didn't know if they would be willing to help anyways—help the Sakurazukamori, help a Dragon of Earth, even though this was _Subaru_ and he had never actually fought them, not _really,_ just standing next to Fuuma and not doing anything to help either side. Sometimes Kamui would delude himself, late at night when he couldn't fall asleep, that Subaru had looked at him with something more than the total indifference that had taken over him. It didn't have to be liking; he would even settle for hate, because all he wanted was for Subaru to feel. Something. Anything.

He knew it was a lie, of course, and that the dreams would just make it that much worse the next time they faced off; but somehow, he couldn't quite stop. He would still ache either way, he thought, so why not try to squeeze out what little consolation he could?

Even staying with Subaru like this, watching him toss and turn in his sleep while being completely unable to help him, was an exercise in masochism. He had known the other man had nightmares—who passed under the mansion's roof that didn't?—but either the fever exacerbated them or they had gotten worse since Rainbow Bridge. Probably both.

He didn't _have_ to stay and watch Subaru's uneasy sleep, at least not in the literal sense of the word. The fever had broken a while ago—or, at any rate, the little numbers on the thermometer he had managed to dig out of a bathroom cupboard downstairs had finally started to go down—and, though his medical knowledge was practically nonexistent, he was fairly certain that simply having another person in the room did nothing to speed the healing process. Technically, it would make perfect sense for him to go take a nap in one of the guest bedrooms or something.

In reality, of course, Kamui was all but welded to Subaru's side (and there was another image that he was _not thinking about_, dammit), and he was capable of leaving the room like he was capable of building a nuclear reactor from rusty car parts, so he stayed and stared and blushed and hated himself for following the line of Subaru's stomach as it disappeared beneath the crisp linen sheets.

He was so caught up in his web of Subaru and trepidation and self-loathing, he didn't even notice when he nodded off.

Naturally, Fate dictated that the chair he had pulled up beside the headboard be angled _just so_.

* * *

"Kamui?"

A voice, Kamui thought fuzzily. Saying his name. Quite a pretty voice too… but it didn't sound happy. Not sad, but not happy. He didn't like that. He wanted the voice to be happy.

"Be 'appy," he ordered groggily.

A long pause. "Kamui, you're asleep," the voice explained patiently. "You don't know what you're saying. Are you ready to wake up?"

Kamui took a moment to examine the statement. The entire world seemed to be a giant black hole, which meant that he had his eyes closed, at least; but his state of wakefulness was irrelevant. The voice should be happy, he was sure of that much. He wanted it to be happy. Who was the voice, anyways? It sounded like… like…

_Subaru._

Oh, _shit._

Kamui's eyes flew open, and he realized with a wave of mortification that he had fallen asleep _on Subaru,_ his upper body sprawled out over Subaru's (_bare,_ his mind added helpfully) chest.

"Sorry!" he yelped, frantically pushing himself off the bed and backpedaling across the room. "Sorry, sorry—" He mentally rewound the conversation that had just taken place, and another rush of color hit his cheeks. "Sorry!" Oh, god, what did Subaru think of him now? He had practically _stripped_ him while he was unconscious, put him in his own _bed_—and that just had to look _so_ bad—and now he went to sleep on him! Subaru probably hated him now, regretted ever coming—and he hadn't meant to come in the first place, he had been sick and dreaming and looking for his stupid_Seishiro-san,_ and—

"Kamui? Is something wrong?"

Kamui's head snapped up and he looked at Subaru with slightly desperate eyes. Subaru didn't _sound_ mad. He sounded…

Well, empty. Maybe a little confused, but not _really,_ as though anything Subaru felt was like the soapy water of a bubble floating on the air—insignificant, barely a drop of liquid, but stretched and warped and ultimately defined by the hollowness beneath it; so easy to break, to puncture, to watch in horror as it collapsed into itself, entire existence shattered by a child's careless touch.

And Kamui was a child, still.

"Ah, no, nothing." Everything. "I'm really sorry I fell asleep on you," he added miserably. "I didn't mean to."

"It's not a problem," Subaru said. "You haven't been sleeping properly?"

Kamui considered pointing out the blatant hypocrisy of the question, given that he hadn't been the one who showed up soaked with rainwater and delirious on the doorstep of a group of people who may or may not have been inclined to kill him on sight, but this was _Subaru_ after all and he really knew better than to expect him to take care of himself. Besides, Kamui still hadn't quite managed to stop stammering enough to string out a proper reproach. "Kinda."

That was a _no,_ and they both knew it. "Ah," said Subaru, as if that most unhelpful of all syllables meant something—and knowing Subaru, it probably did, although Kamui didn't have the slightest idea what.

"Yeah." His _tell Subaru everything_ habit was starting to kick in, and he so nearly said: my nightmares have gotten worse too, I don't know what to do about Fuuma, I don't think I can beat him, I need—

_You,_ but that would be too much, far too much, and he locked his jaw against the words.

"You have to…" Subaru began halfheartedly, then gave up on the idea altogether. "Why not?" He noticed the papers lying around the bed, and asked, "School?"

School? This was the first time Kamui had so much as cracked a textbook in ages—specifically, the number of ages it had been since… well, since Subaru left. "Ah, no. I… haven't been so worried about that, lately." He kept that fact that the decline in his already meager interest in studying had coincided with the absence of his tutor to himself.

"Why, then?"

Kamui opened his mouth to reply with something about Fuuma or nightmares or even the other Seals, and heard himself say, "I miss you."

There was a long, vaguely puzzled silence while Subaru stared at Kamui and Kamui was frozen in horror.

"I'm—I'm sorry!" he managed to squeak out finally. "I didn't mean—it's none of my business—please excuse me!"

Subaru was still looking at him. "You… miss me?" he asked slowly, examining each word as it fell from his mouth. "Kamui… this is who I am now. It was Se—it was a Wish, and my choice. I chose this. I… did not mean to hurt you, but I cannot undo that choice, now. Even if I could… I apologize, but I could not. Would not." He touched his right eye absently, and Kamui noticed that it was the same color as the Sakurazukamori's. He hadn't noticed it before, somehow, but now… did that mean…

Oh. Oh, _ew_.

Kamui dropped his eyes to the ground as he fought to quell his nausea. After a struggle to be certain that he could speak without retching on Subaru, he ventured, "But… why? I mean, I know—I can guess—why you chose it, but why… why is this the first time I've seen you—talked to you since then? Is that some kind of rule, that the assassin can't have friends?"

Silence. Right when Kamui started to think that it was horribly presumptuous of him to assume that Subaru would _want_ to talk to him, would go out of his way to speak to a moody teenage boy who couldn't even manage to save the world properly, Subaru asked, "You would like for me to visit?"

"Yes!" Kamui replied instantly, forcing himself not to blush because if there was even the slightest chance that he could get to see Subaru again, he would descend to any level of pathetic desperation to achieve it. "Yes, of course! Why wouldn't… oh. Still, why wouldn't I?"

Subaru stared at him, the cautious stare of someone who is wondering whether they should go with the obvious answer or not, and _that_ was more like the Subaru he remembered, at least a bit. "Umm…"

Kamui sighed, shaking his head impatiently. "You're still _Subaru,_ don't you get it? I knew about you and the Saku—and the old—and _that guy_ before I had even really met you in person, remember, and this is just kind of an extension of that." Like hell he was going to call the man 'Seishiro-san.' "I mean, you don't have to talk to me or do anything if you don't want to, but—yeah, I'd like it." He paused, then added, "A lot."

Subaru's stare was really beginning to unnerve him. After another long silence, Subaru looked down at the gloves Kamui hadn't dared to take off and asked hesitantly, almost helplessly: "Would Seishiro-san have wanted it?"

Some tiny hope in Kamui's heart shattered. Everything with Subaru began and ended with that man, even more so when he was dead than when he was alive. "I don't know," he replied truthfully, bile rising in his throat at the brutal honesty, more brutal to himself than to Subaru. "I don't think he'd want you to kill yourself like this, though. And I think… I think that as long as you still"—_love him—_"are his, he wouldn't care what you did."

Subaru tilted his head, childlike and yet not. "But I'll _always_ be his," he said plainly, as though this fact should have been evident to the world—which it was, of course, though apparently the old Sakurazukamori didn't see it as such.

"Yes," Kamui agreed quietly. "Yeah, I know. So I don't think he'd mind. Unless you would?"

Subaru hesitated, as though the very idea of having desires for himself was foreign to him, and then shook his head. "I wouldn't. I'd like for you to be happy. Would it make you happy?"

"… Yeah. It'd make me happy."

"Then shall I come back later?"

Something in Kamui's throat caught, and he didn't know if it was in happiness or pain. "… Sure. I don't know if Sorata and Karen and—"

"They won't see me, then," Subaru said, shrugging, as if sneaking into one of the most warded and protected buildings in all of Japan was an everyday thing for him. Maybe it was. Kamui didn't know exactly what assassins did by way of sneaking, but it was probably impressive.

"Okay."

"Thank you for your hospitality."

Kamui blinked, about to point out that Subaru was still probably sick because he couldn't have been asleep _that _long, and anyways he had been going to make him something to eat, when the man just vanished.

Probably a Sakurazukamori thing, he decided after picking his jaw back up off the floor. One of his notes, blowing around in the eddies of wind caused by Subaru's departure, caught his eye.

_Force equals mass times acceleration._

_Mass: infinite._ Kamui can do nothing to help Subaru get over the old Sakurazukamori; he knows better than to try. Subaru is… irretrievably lost, in that sense, and all that trying to talk him out of his obsession would do would be to drive him even farther away.

_Acceleration: gaining._ Falling, when gravity is pain and the ground is death, and Subaru seems to be rushing toward that end as quickly as he could drive himself to it.

_therefore, Force: beyond reckoning and beyond repair. But isn't that what it is to love?_ Maybe Kamui won't be able to help Subaru, in the end; maybe the other man will forget his promise (and he never really _promised_), maybe he will allow himself to fall anyways. The most Kamui can hope to do is cushion the fall—but he will hope.

And maybe hope will be enough, after all.

* * *

Yeah, um... Angst. And very shaky characterization, and gratuitous abuse of the italics button-- though I always tend to think that my characterization is shaky. Why must Subaru be so... so... Subaru?

Criticism welcomed. Really. I like knowing what I've messed up on. (Though praise is also wonderful, of course.)


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